Underwater well completion method and apparatus



Jan. 14, 196 9 J, FOWLER ET AL UNDERWATER WELL COMPLETION METHOD ANDAPPARATUS Filed Aug. 15. 1966 Sheet INVENTORJ (foil? /7. Few/er flay/aI? Hera Jan. 14, J. FQWLER ET AL.

UNDERWATER WELL COMPLETION METHOD AND APPARATUS Filed Aug. 15, 1966Sheet 2 M11 I N VEN TORJ Jan. 14, 1969 J. H. FOWLER ET AL 3,421,580

UNDERWATER WELL COMPLETION METHOD AND APPARATUS Filed Aug. 15, 1966Sheet 3 of 11 INVENTORJ c/b/7/7 Faw/er fla /0 f? Hera Jan. 14, 1969 jFQWLER ET AL 3,421,580

UNDERWATER WELL COMPLETION METHOD AND APPARATUS Filed Aug. 15, 1966Sheet 4 r 11 INVEN'IORS Jafin f7. Few/e r .00 v/a P. Her 0 Jan. 14, 1969I J. H. FOWLER ET AL 1 3,421,580

UNDERWATER wELL COMPLETION METHOD AND APPARATUS Filed Aug. 15, 1966 7 VSheet 5 of 11 INVENTORJ db/lw h. few/er flax l0 f. Herd UNDERWATER WELLCOMPLETION METHOD AND APPARATUS Filed Aug. 15, 1966 33 Jan. 1-4, 1969 JFOWLER ET AL Sheet INVENTURS cfofin h. Few/er flav/c/ "P Hera Jan. 14,1969 J, FOWLER ET AL UNDERWATER WELL COMPLETION METHOD AND APPARATUSSheet 1 Filed Aug. 15, 1966 INVENTORS Few/er 7 0 w a P. Hera Jan. 14,1969 J. H. FOWLER Em 3,421,58

UNDERWATER WELL COMPLETION METHOD AND APPARATUS H Sheet 8 of 11 FiledAug. 15, 1966 .Z, a a Z M A a! 4%. III 1 Y A.

Jan. 14, 1969 J. H. FOWLER ET UNDERWATER WELL COMPLETION METHOD ANDAPPARATUS Sheet 9 of 11 Filed Aug. 15,

Jan. 14, 1969 J. H. FOWLER ET AL 3,421,530

'7 UNDERWATER WELL COMPLETION METHOD AND APPARATUS Filed Aug. 15, 1966Sheet /0 of 11 'INVEN'TORS (fa/1x7 f1. fbw/Ev 170100 l Herd Jan. 14,1969 F E ET AL 3,421,580

UNDERWATER WELL COMPLETION vMETHOD AND APPARATUS Filed Aug. 15, 1966Sheet of 11 INVENTORS Jb/W? h. FQW/EV 17:? W0 P. Herd United StatesPatent 3,421,580 UNDERWATER WELL COMPLETION METHOD AND APPARATUS John H.Fowler and David P. Herd, Houston, Tex., as-

signors to Rockwell Manufacturing Company, Houston,

Tex., a corporation of Pennsylvania Filed Aug. 15, 1966, Ser. No.572,599

U.S. Cl. 166.5 40 Claims Int. Cl. E21b 33/035; E21b 43/01; E21b 7/12ABSTRACT OF THE DISCLOSURE Method and apparatus for underwater wellextended casing completion. The method comprises the steps of installinga conductor pipe with a well head attached above the mudline, attachinga conduct-or riser to the well head extending to above the watersurface, drilling holes for other casings and suspending them withrisers attached thereto in the well head by hanger-heads, cementing theother casings in place. At this point the well may be immediatelycompleted by installing an above water production tree or an underwaterproduction tree or temporarily abandoned by packing-off the annularspaces between each hanger-head and capping the well at the Wall headand later completing above water or underwater, or the well may even bepermanently abandoned. Each of the inner casings is supported by ahanger-head which is in turn supported by another hanger-head, the lastbeing supported by the well head. Some of these hanger-heads have ductsthrough their walls with openings above and below their support surfacesto allow cement fluid returns. The hanger-heads are connected to theirrespective risers by back-ofi joints for easy disengagement. Oneback-otf joint disclosed requires only a fraction of a turn fordisengagement. Its connection means comprises a plurality of alternatingtooth segments and smooth wall segments cooperatively engaging similarsegments on its respective hanger-head. When the risers and back-offjoints are removed the pack-off may be remotely installed in the annularspaces between adjacent hanger-heads. The pack-off may also utilize thequick connection design of the back-off joint; i.e., the alternatingtooth and smooth wall segments. One pack-elf embodiment comprises atubular attachment means and a tubular seal means rotatably attached.The pack-01f is inserted in the annular space between hanger-heads. Theattachment means is connected through the quick connection toothsegments to one of the hanger-heads. The seal means is compressedsealing the annular space. The pack-offs are removable for replacementof risers, or for other reasons if required.

This invention relates to underwater drilling of oil and gas wells andpertains more particularly to methods and apparatus used in underwaterextended casing operations.

Increased activity in offshore drilling has led to continued search forbetter methods and apparatus in this area. To cope with some of theproblems of underwater drilling, various extended casing methods havebeen developed. Extended casing methods, basically, have a wellconductor anchored to the ocean floor which provides support to aspecial underwater well head. This well head in turn supports a multiplenumber of hanger-heads, hangers and their respective casing strings. Thedrilling platform is thus relieved of much of the structural supportresponsibilities required in other methods. Casing is then extended fromthe underwater well head to the drilling platform where conventionalwell head equipment may be used during drilling. After drillingcompletion, the well may be permanently abandoned, tem- Patented Jan.14, 1969 "ice porarily abandoned or immediately completed forproduction. If temporarily abandoned, the extended casing may beremoved, the exposed casing annuli enclosed in a protective cap and thedrilling platform removed. Thus, the underwater well head is free fromthe hazards of ocean going traflic and structural support problems. Apermanent production platform may at some later time be installed, theprotective cap removed, casing extended to the permanent platform, andconventional production well head equipment permanently installed.

Of course, if immediate completion is desired it will not be necessaryto remove the extended casing and install protective cap, etc.

As can be seen from the foregoing discussion several advantages of theextended casing method of drilling are apparent. However, some problemsarise in the use of such methods. Some of these problems are:

(1) Providing for suspension and pressure loads.

(2) Providing continuous casing annulus flow for cementing, etc.

(3) Providing sealing and pack-off means underwater.

(4) Protecting exposed casing and equipment from under- Waterenvironment.

(5) Providing easy trouble free remote underwater connections.

The present invention attempts to solve these problems.

It is, therefore, a primary object of the invention to provide methodsof extended casing completion which may be performed remotely allowingpermanent abandonment, temporary abandonment or immediate completion ofwells.

Another object of the invention is to provide underwater well headapparatus which may be remotely installed and connected throughmechanical means.

A further object of the invention is to provide casing hanger apparatusin well heads which support casing string loads and allow continuousannular flow.

Still another object of the invention is to provide effective pack-offand sealing means for underwater well heads which may be quickly,easily, and remotely installed or removed.

Still another object of the invention is to provide a tool which may beeasily adapted to set, test, and remove underwater pack-oif and sealmeans of different sizes.

Still another object of the invention is to provide an underwater wellhead of the extended casing type which may be adapted to receiveextended casing and alternately have such extended casing removed andreplaced by pack-off and cap assemblies which protect the well bore fromexposure to the underwater environment.

A preferred embodiment of the method and apparatus which are the subjectof this invention, and by which the foregoing objects and other objectsare attained, is shown in the accompanying drawings and in the followingdescription. As will be seen, the apparatus described embodies versatilestructure which is readily used for a variety of purposes. Thus, thehanger-heads which are comprised in the underwater well 'head of theembodiment disclosed are suitable for supporting casing strings duringdrilling and cementing operations, and for supporting risers from thesecasings to the surface of the water. The hanger-heads are also designedto allow fluid flow through the hanger-heads between concentric stringsof easing.

A quickly and easily connectable and releasable backotf joint isprovided for connection or disconnection of riser casings. The back-offjoint connection is also readily adapted to aflixing the pack-0E in theannulus between two concentric casing strings. In addition, this sameconnection provides a highly satisfactory connection for a tubing head.

A pack-off assembly is provided which is easily inserted in the annulusbetween concentric casing strings, and which is just as easily removedin the event that it is later decided to open such annulus.

The back-off joint in the hanger-head is also suitable for readyconnection of a cap in the event that the well is to be capped fortemporary abandonment.

Furthermore, a novel tubing head and tubing hanger is provided which isparticularly adapted for installation in remote locations.

For a better understanding of the invention, reference is now made tothe following description and to the accompanying drawings, whereinFIGURE 1 is a somewhat schematic elevational view showing a drilling rigand platform in place, with casing and extended casing therebelow, thedrilling rig and platform being purposely made small in proportion;

FIGURE 2 is a vertical sectional view of one embodiment of casingsupport apparatus according to this invention;

FIGURE 3 is a vertical sectional view of one embodiment of casingsupport apparatus according to this invention, showing the casing packedoff;

FIGURE 4 is a vertical sectional view of one embodiment of casingsupport apparatus according to the invention, showing the welltemporarily abandoned;

FIGURE 5 is a vertical sectional view of one embodiment of casingsupport apparatus according to the invention, showing tubing in place;

FIGURE 6 is half-sectioned elevational view of a hanger-head andback-off joint embodying the invention;

FIGURE 7 is a sectional view of the hanger-head and back-off joint shownin FIGURE 6, taken at line 77 of FIGURE 6;

FIGURE 8 is an elevation in partial-section of a hangerhead and back-offjoint embodying a modified form of the invention;

FIGURE 9 is a horizontal section taken along line 9--9 of FIGURE 8;

FIGURE 10 is a fragmentary sectional view showing latch means embodiedin the invention;

FIGURE 11 is a fragmentary horizontal section taken along line 11-11 inFIGURE 10;

FIGURE 12 is a vertical sectional view of pack-off means embodied in theinvention taken at line 12-12 of FIGURE 13;

FIGURE 13 is a top view of the pack-off means of FIGURE 12;

FIGURE 14 is an elevational view, partly in section, of a running toolsuitable for setting some of the apparatus of this invention;

FIGURE 15 is a fragmentary sectional view of a portion of the runningtool of FIGURE 14, showing it engaged with a pack-off;

FIGURE 16 is a half-section view of a pack-off with a running toolengaged in it, showing the pack-off in position between twohanger-heads;

FIGURE 17 is a horizontal sectional view of the apparatus of FIGURE 16,taken at line 17-17 of FIG- URE 16;

FIGURE 18 is a fragmentary sectional view of a portion of the apparatusshown in FIGURE 8; and

FIGURE 19 is a horizontal half-section of the running tool shown inFIGURE 14 taken along line 1919.

FIGURE 1 of the drawings portrays schematically, in

reduced proportion, a drilling rig 10 mounted upon a drilling platform11 above the water line 12. A conductor riser 23 extends from the abovethe water line to near the mud line 13 and is surmounted by a landingbase 14 which in turn supports conventional casing heads indicatedgenerally at 15. The lower end of the conductor riser 23 is supported onan underwater well head 21, which in turn is supported on a conductorpipe 20 which comprises surface casing for the well.

For the most part, the apparatus described hereinafter is apparatuswhich is carried within, comprises a part of, or is immediately adjacentthe well head 21. The methods of operation to be described and theapparatus for performing such operations will principally be discussedin terms of the use of a casing program involving a series of fiveconcentric casings which, for the purpose of this discussion, may bedescribed as 30 inch, 20 inch, 13% inch, 9% inch, and 7 inch casings. Itwill be apparent, however, that the methods and apparatus of thisinvention may be used equally well with other casing sizes and withdifferent numbers of casings in which the same principles of operationwould apply.

The conductor pipe 20 is normally driven or jetted into place, but maybe run in a drilled hole if bottom conditions require it. It should benoted that large bending moments may be exerted at approximately the mudline due to water currents, offsets of risers, mud weights, etc. Forthese reasons, it has been found to be desirable to provide heavier wallpipe beneath the well head 21 for a short distance, such as about 10feet.

In operation, the 30-inch conductor pipe 20 is installed with the wellhead 21 and the conductor riser 23 attached thereto. As shown in FIGURE2 the well head 21 in the embodiment shown consists of an upper hubmember 22, which may be welded or otherwise connected to the conductorriser 23, a lower hub member 24 welded or otherwise connected to theconductor pipe 20, and a clamp 25 which connects the hubs 22 and 24together. The hubs are provided with end flanges 22a and 24a,respectively, which are tapered on the back for engagement by a splitclamp 25 which is generally U-shaped in cross-section and has taperedinwardly turned faces proportioned for a tight engagement with theflanges 22a and 24a when they abut each other. The clamp 25 may, forexample, be in two semi-circular pieces which are held together as bymeans of bolts 25a. Seal means are provided between the flanges 22a and24a as by means of, for example, an O- ring seal 26 and a metal-to-metalseal formed by a tapered extension 27 on the end of flange 22a and acorrespondingly tapered bore 28 formed in the end of flange 24a.

An inwardly turned shoulder 29 in the bore of hub 24 comprises anupwardly facing support surface within the well head 21 for supportingother elements as will hereinafter be described.

Following the setting of the 30" conductor casing a hole for 20" surfacecasing is next drilled and reamed, and the 20" surface casing 30 is runin place, landed, and cemented. Surface casing 30 is suspended in wellhead 21 on support means 29 by means of support lugs 34 spacedcircumferentially around the periphery of a hanger-head 32. Riser 31 isconnected to the upper end of hanger-head 32 through back-off joint 33.Riser 31 extends to the surface where it is connected and sealed to aconventional 20" lower casing head, as indicated in FIG- URE l. Thelower casing head may serve as a landing base for a conventional 20%"blowout preventer, as is well known in the art. Casing head seal andblowout preventers may be tested at this time.

Referring to FIGURES 6 and 7, hanger-head 32 and back-ofl joint 33 areshown in detail. Hanger-head 32, conveniently cast in one piece, has agenerally cylindrical exterior with a generally cylindrical openingtherethrough. Near the longitudinal base of its exterior surface,support lugs 34 are radially disposed at regular intervals leavingpassage means 36 therebetween. Passage means 36 are enlarged by castingrecesses 36a in the wall of hanger-head 32 as shown by phantom lines. Abeveled surface 35 is machined on the lower edges of support lugs 34 tocooperate with the beveled shoulder of support means 29 (see FIGURE 2).At the interior base of hanger-head 32 pipe connection means 37 isprovided in the form of threads. Near the interior longitudinal center,

support means 38 is provided in the form of a circumferentially beveledshoulder. The inside diameter of hanger head 32 is enlarged upwardlyfrom support means 38 to allow easy passage of hanger-head 52 which issup ported at support means 38 (See FIGURE 2). Breechlocking means 39 isprovided at the upper interior of hanger-head 32 and the exterior ofback-off joint 33.

The breech-locking means function similarly as a breech-block in, forexample, a naval gun. A plurality of longitudinally extending toothsegments 40 are machined on alternate BO-degree segments of the exteriorof the back-off joint 33, the arcuate length of the teeth being slightlyless than 30 degrees and the upper flanks of all the teeth being beveledat the ends as shown at 40a. Matching tooth segments 41 are machined inthe upper interior of hanger-head 32. These teeth also have a lengthslightly less than 30 degrees. The teeth shown are generally in the formof a buttress thread, but it will be appreciated that other forms can beused. The teeth 41 have, in the embodiment shown, beveled portions ateach end on the lower sides of the teeth.

The teeth are engaged with each other by lowering the back-otf jointinto the hanger-head with the tooth segments 40 positioned to passbetween the tooth segments 41. The lowest tooth 42 in the back-off jointhas a double thickness, and the lowest groove 43 in the tooth segments41 has a double Width, so that the back-off joint must be lowered farenough to engage the double thickness tooth and the double width groove.The back-01f joint may then be rotated 30 degrees to engage thebreech-locking means. The teeth do not have any lead angle, but they arepulled tightly into engagement by means of the bevels 40a on the ends ofthe teeth 40 and the corresponding bevels on the ends of the teeth 41.

Sealing is obtained between the back-off joint and the hanger-head bymeans of an O-ring 45 positioned around the back-off joint just abovethe tooth segments 40. In order to prevent the back-off joint andhanger-head slipping with relation to each other during the time theyare being lowered into the well, they are held together by means of ashear pin 44.

If, after the hanger-head 32 with its associated casings having beenpositioned in the well, it is desired to remove the back-off joint 33,this may be done simply by twisting the riser casing 31 to the right.This twisting force to the right will shear the shear pin 44 andmovement of the back-off joint 30 degrees will disengage the teeth 40from the teeth 41. Rotation of the back-off joint with relations to thehanger-head is stopped atfter 30 degrees by means of a stop comprising akey 46 mounted in a milled slot on the back-off joint 33 in such a wayas to contact the end of a key slot 47 on the upper end of thehanger-head 32.

Female threads 49 in the upper end of the back-off joint provide meansfor connection to the riser casing 31.

Referring now to FIGURE 2 again, after the 20" casing has been set, ahole is drilled for 13%" casing 50, and the casing is run, landed andcemented in a conventional manner. Hanger-head 52, back-off joint 53,and riser 51 are shown made up in their proper places. The 13 /8 riser51 is extended to the surface and packed oif in a conventional manner(not shown). The 20%" preventer is removed, 13%" x 20" surface pack-offinstalled, a conventional intermediate casing head installed, andpack-off tested. 12" preventers are then installed and tested.

Referring now to FIGURES 8 and 9 hanger-head 52 is shown in detail.Hanger-head 52 is generally cylindrical on its exterior and has agenerally cylindrical opening therethrough. The center portion ofhanger-head 52 has an outside diameter substantially greater than theend portions. This results in a thicker wall to allow for integralpassage means 61 in the form of ducts. These ducts 61 arecircumferentially disposed and extend longitudinally through the wall asshown in FIGURES 8 and 9 to allow passage of fluid around anotherhanger-head 72 (to be described later) which is suspended on theinterior wall of hanger-head 52 (see FIGURE 2). The interior wall nearthe center of hanger-head 52 is provided with latch support means 54 inthe form of two circumferentially machined grooves which will cooperatewith latch means (to be explained later) to support hanger 72 and itsattached casing 70 (see FIGURE 2).

At the exterior base of the larger diameter center portion ofhanger-head 52 support ring 55 is welded. At regular intervalscircumferentially disposed passage means 55a are provided between thering 55 and the body of the hanger-head 52. Support ring 55 has abeveled downwardly facing surface 56 on its outer edge which isproportioned to engage support means 38 on the interior of hanger-head32 (see FIGURE 2). This allows passage of fluid between hanger-head 32and hanger-head 52. At the interior base of hanger-head 52 pipeconnection means 57 are provided in the form of threads for engagementwith cooperating threads on the upper end of casing 50.

At the upper interior of hanger-head 52 tooth segments 58 are providedto cooperate with tooth segments on the exterior of back-off joint 53 toprovide breech-locking means which in many respects is similar to thebreechlocking means of hanger-head 32.

However, this breech-locking means is useful for several differentfunctions, and therefore comprises some features not found in thebreech-locking means of hangerhead 32.

FIGURE 8 shows hanger-head 52 with back-off joint 53 installed thereinand with riser 51 threaded into the back-off joint. As shown, aplurality of longitudinally extending tooth segments 240 are machined onalternate 30-degree segments of the exterior of the back-off joint 53,the arcuate length of the teeth being slightly less than 30 degrees. Theupper flanks of the teeth in tooth segment 240 are beveled at the endssimilarly as the teeth in the tooth segments 40 previously described.The lowest tooth 252 is approximately twice as thick as the others.Matching tooth segments 241 are machined in the upper interior of thehanger head 52, with the lowest groove 253 twice as wide as the othersfor engagement by doublethickness tooth 252. These teeth also have anarcuate length slightly less than 30 degrees and have the beveledportions on the lower flanks of the teeth at each end.

The teeth shown are generally in the form of buttress threads, but itwill be appreciated that other forms of teeth can be used.

Spaced substantially below the tooth segment 241, the hanger-head 52 hasan inwardly turned support shoulder 242. Intermediate the supportshoulder 242 and the tooth segments 241, the back-oif joint 53 sealinglyengages the hanger-head. The sealing means includes two O-ring seals 243and 244 which are positioned in suitable grooves around thecircumference of the back-off joint below the teeth 240 of the back-01fjoint. Intermediate the O-rings 243 and 244, the back-off joint istapered, as shown in FIGURE 18 at 245, to engage a cooperating taper 246formed in the bore of the hanger-head 52. A run-out groove 247 isprovided at the small end of taper 245 and a similar run-out groove 248is provided at the large end of taper 246.

The upper end of the hanger-head 52 is provided with a plurality,preferably six, stops 249, positioned for engagement by keys 250 whichare positioned in slots 251 milled in the outer edge of the back-offjoint and which extend downwardly therefrom far enough to fit betweenthe stops 249.

The back-off joint will normally be assembled in the hanger-head at thesurface before lowering into the well. This is accomplished by merelyinserting the back-off joint into the hanger-head with the toothsegments 240 aligned with the spaces between the tooth segments 241 andmoving the two members together until the large double thickness tooth252 is positioned opposite the double width groove 253. At this point,the tapered surfaces 245 and 246 will be substantially in engagement.The back-off joint may then be rotated 30 degrees to the right to engagethe tooth segments 240 with the tooth segments 241. The beveled topflanks of the teeth of segment 240 engage the beveled bottom flanks ofthe teeth of segment 241 to cause the back-01f joint to be pulled downfurther into the hanger-head so as to force tapers 245 and 246 intosealing engagement with each other as the back-off joint is rotated intoposition. A shear pin 254 (see FIGURE 2) is then inserted to hold therelationship of the back-off joint and the hangerhead. The elements maythen be lowered into the well.

When it is desired to separate the back-off joint from the hanger-head,it is merely necessary to apply a righthand twisting force to the casingriser 51 so that the shear pin 254 is sheared. The back-off joint willthen rotate 30 degrees until it is stopped by the engagement of the key250 with the stop 249. The back-off joint may then be removed by merelylifting straight up.

Referring again to FIGURE 2, when the 13 /3" casing is in place, a holefor the 9% casing 70 is drilled. The 9 /8" casing string 70 is run inthe hole with hanger-head 72, back-off joint 73, and riser 71 properlymade up. The casing string 70 is then cemented in a conventional manner.The riser 71 is extended to the surface where the 12" preventer isremoved and 9 /8" x 12" surface packing installed. A conventionalintermediate well head is installed and tested. A preventer is nextinstalled and tested.

Hanger-head 72 is similar to hanger-head 52 of FIG- URE 8 except thatthe function of support ring 55 of hanger-head 52 is performed by latchmeans 80, which can best be described with reference to FIGURES 10 and11. Latch means 80 basically consists of latch segments 81, segmentgroove 82, guide means 83, retainer ring 84, and spring means 85. Latchsegments 81 are conveniently made by machining a ring whose profile isthat shown in FIGURE 10; then cutting the ring into four segmentsslightly less than 90 degrees each. The segments are mounted in segmentgroove 82 which is circumferentially machined on the exterior ofhanger-head 72. Guide means 83 consists of a vertical bar 86 attached tothe inner face of latch segments 81 by screws 87. The ends of verticalbar 86 ride in guide channels 88 which are radially machined on the topand bottom of latch groove 82 at 90 degree intervals. Latch segments 81are forced radially outward by spring means 85. The configuration of thelatch segments is such that they will not be forced out into any recessabove the hanger-head 52.

Upon downward movement of hanger-head 72 within hanger-head 52 latchsegments 81 automatically engage support means 54 to support suspensionload.

To disengage latch means 80, hanger-head 72 is simply moved upwardly,causing the latch segments 81 to move radially inwardly due to thecooperating beveled upper surfaces of the latch segments 81 and supportmeans 54. The lower ends of vertical bars 86 engage retainer ring 84 toprevent the latch segments from being forced out of segment groove 82 bythe springs 85.

Back-off joint 73 is similar in construction to back-off joint 53,except that it is dimensioned smaller.

In the next step, referring again to FIGURE 2, a hole is drilled for 7"inner casing 90. The casing 90 is then made up with hanger-head 92 andback-off joint 93 in their proper places. Riser 91 is extended to thesurface. Cementing is then completed normally. Hanger-head 92 is similarto hanger-head 72 except that no integral passage means are requiredsince this is the last casing string. Back-off joint 93 is similar toback-off joints 53 and 73 as previously described.

At this stage of procedure several alternatives are possible. The wellmay be immediately completed, temporarily abandoned, or permanentlyabandoned.

If the well is to be immediately completed the next step is to remove,at the surface, the 10" preventers, install a 7" x 10" surface pack-off,install a 10" x 6" tubing head equipped with 7" bottom pack-off andtest. A 6" preventer would then be installed and tested, casingperforated, tubing run, pack-off installed and back pressure valvesinstalled. The preventer would then be removed, a production treeinstalled and tested, and the Well brought in. All of these proceduresand equipment are conventional and, therefore, need no description.

However, if the well is to be temporarily abandoned, in the next stepall perforations will be squeezed off and one or more bridge plugs run,set and tested in the 7 casing in a conventional manner. The 6"preventer 10" x 6" tubing head and 7" x 10" surface pack-off will beremoved. The 7 riser 91 and back-off joint 93 will then be rotatedapproximately 30 degrees clockwise, shearing a shear pin such as shearpin 44 as shown in FIG- URE 6. Rotation is limited to 30 degrees by stopmeans such as 46 and 47 in FIGURE 6. Thus, the breech-locking means isdisengaged and 7" casing 91 may be elevated and removed along withback-off joint 93. Again at the surface the 12" x 10" intermediatecasing head and 9% x 12" surface pack-off is removed. As previouslydescribed for 7" riser 91, the 9 /3" riser 71 is rotated 30 degreesclockwise and removed along with back-off joint 73.

At this point, a 7" x 9 /3" pack-off means will be run. The pack-offmeans is run by attaching it to a suitable tool 200 at the surface andlowering it on a pipe string to engage the breech-locking means inhanger head 72 as hereinafter described and as shown in FIGURE 3.

Referring to FIGURES 12 and 13, pack-off means 100 will be described indetail. Pack-off means 100 consists basically of two major assemblies,an upper section which locks and holds the pack-off down, and a lowersection which contains the sealing element. These two sections canrotate in relation to each other.

Upper section 120 is generally cylindrical in shape. On its exterior,alternate rows of tooth segments 103 and smooth wall segments aremachined at 30 degree intervals. Tooth segments 103 are similar to toothsegments 58 on back-off joint 53 in FIGURE 8, and therefore require noadditional description. On the upper exterior of upper section 120 acircumferentially extending shoulder 102 is provided on which ring 101sits. Ring 101 is annular in shape and has six lugs 101a extendingradially outwardly at 60 degree intervals. It is held to upper section120 by two oppositely disposed pins 101b, which are inserted throughpack-off ring 101, the end of which rides in arcuate slots 1010 machinedin 30 degrees of the exterior circumference of upper section 120. Theinterior of upper section 120 is provided with longitudinally extending45 degree tool slots 112 intersecting an annular tool groove 112a, whichprovides J slot engagement for running tool 200 to be described later.Secondary seal means 104 in the form of an O-ring is mounted in a groovenear the exterior base of upper section 120. Slot 113 is machined on theupper edges of upper section 120 and ring 101 to provide for a key onthe running tool, to be explained later.

Lower section 130 consists of upper cylindrical retainer ring 106, lowercylindrical retainer ring 108, primary seal means 107 therebetween, andconnection means comprising cap screws 109 Whose heads are counter-sunkin the lower end of ring 108. Seal 107 is made of a resilient materialsuch as rubber, and is adapted to seal on both its inner and outercircumferences when compressed between retainer rings 106 and 108.

Referring now to FIGURES 14 and 19, the pack-off running and pullingtool 200 will be described. It has three major assemblies, guide means205, plug means 204 and engaging means 220.

Guide means 205 has steel ribs 205a extending radially from a shaft205]) so that the outside diameter of the rib edges is slightly lessthan the inside diameter of the innermost hanger-head 92 (see FIGURE 3).Guide means 205 on entering hanger-head 92 aligns the tool 200 andpack-off means 100 vertically and horizontally. At the upper end of toolshaft 212, connection means in the form of threads 213 is provided. Atest port 214 is drilled radially through the shaft to communicate witha 'hollow portion 214a of the tool, the bore of engaging means 220, andthe pipe string to which tool 200 is connected.

Near the middle of tool 200 is a plug means 204 which is cylindrical inshape, its outside diameter being such as to fit with a slight clearancein the inside diameter of the upper portion of hanger-head 92. An O-ring207 seals between the plug 204 and the tool shaft 212. Mounted at thebase of plug means 204 is a seal means consisting of a floating ring202, a retainer ring 203 and Orings 208, 209, and 210. This type designwill provide effective sealing even if slight eccentricity ofhanger-head equipment exists, since O-ring 208 allows the ring 202 tofloat within certain tolerances. Ring 202 is held on plug means 204 bylower retainer ring 203 which is threaded to run on a lower threadedportion of plug means 204. Set screw 211 holds retainer ring 203 inplace. Plug means 204 is mounted on the tool shaft 212 by a pin 201which is inserted in a hole 201a passing through plug means 204 and toolshaft 212. Pin 201 is held in place by lock pin 206. Several additionalholes 201b and 201c are provided at different locations on the toolshaft so that plug means 204 may be maintained at the same relativeposition in hanger-head 92 regardless of which pack-off means is beinginstalled.

Engaging means 220 has a body section 221, slip ring 222, bearing means223 and cap means 224. The base of body section 221 has a diameter tofit within the smallest diameter of pack-off means with which the toolwill be used. Near the base of body section 221 four equally spaced 45degree lugs 225 are provided which project outwardly to a diameterslightly less than that of the tool groove 112a in the pack-off means.The diameter of body section 221 in the spaces between lugs 225 is thesame as the base diameter. Just above the lugs 225 the diameter of thebody section is reduced at 221a. At a point above lugs 225 a shoulder226 is provided by further reducing the diameter of body section 221.Slip ring 222 which rests on this shoulder 226 has four 45 degreefingers 227 projecting downwardly at intervals of 90 degrees to a pointslightly above lugs 225. Bearing means 223 rests on slip ring 222. Capmeans 224 which rides on the upper edge of bearing means 223 is attachedto body section 221 by pins 228, thereby holding bearing means 223 inplace. Two 45 degree arcuate slots 229 are cut on the upper surface ofslip ring 222 at 180 degree intervals. Dog point set screws 230 areinserted in the lower flanged portion 231 of cap means 224 at fixedpositions so that the ends of the set screws 230 may ride in slots 229.Slot 232 (see FIGURE is milled on the lower edge of slip ring 222 toprovide for key 233 attached to slip ring 222 'by screw 234. Key 233will also fit into slot 113 machined on the top of pack-off means 100(see FIGURE 12).

Referring now to FIGURES 16 and 17 in setting a pack-off, tool 200 wouldbe inserted in pack-off means 100 with lugs 225 being in tool groove112a on pack-off means 100. Fingers 227 are inserted in tool slots 112(see FIGURE 12) 45 degrees out of phase with lugs 225. A shear pin 235(see FIGURE 14) holds body section 221 and slip ring 222 in thisposition so that the tool lugs 225 remain engaged with tool groove 112a.Key 234 is inserted so that slip ring 222, pack-oil ring 101 and uppersection 120 of pack-off means 100 may not rotate relative to each other.Set screws 230 are inserted so that they rest at the counter-clockwiseends, viewed from the top, of slots 229. The tool and attached pack-offare lowered into the well bore. The lower tooth of the packoff toothsegments 103 will probably come to rest on the upper tooth ofhanger-head 72 tooth segments. The tool and pack-off are then rotateduntil the pack-01f tooth segments line up with hanger-head 72 smoothsegment portions at which time the pack-off drops into the hangerhead.At this point lower section 130 of the pack-01f means contacts shoulder79 in hanger-head 72, compressing seal means 107 and sealing the annularspace between hanger-heads 72 and 92. Tool 200 and the upper section ofpack-off 100 are now rotated clockwise 30 degrees causing the fullengagement of the breechlocking means. At this point the lugs 101a onring 101 have contacted the lugs 77 on hanger-head means 72.

To remove the tool, the pipe string holding it is again twisted to theright until shear pin 235 is sheared, allowing body section 221 torotate relatively to pack-off means 100. Rotation is limited to 45degrees by set screws 230 coming to a stop at the clockwise end of slots229. At this point lugs 225 are now aligned with tool slots 112 onpack-off means 100 and the tool may be removed by simply pullingupwardly.

To remove pack-off means 100, the lugs 225 on body section 221 andfingers 227 of slip ring 222 are first vertically aligned. A shear pinis inserted in holes 236 through cap 224 into slip ring 222 to hold thisposition. Set screws 230 are inserted so that they rest at the clockwiseend of slot 229. Key 233 is removed. The tool 200 is now lowered intothe well bore into contact with the upper end of the pack-off androtated until lugs 225 and fingers 227 are aligned with tool slots 112in the pack-off 100, causing the tool to drop to the lower shoulder oftool slots 112. Suificient clockwise torque is applied to shear theshear pin in hole 236, and the body section 221 is then rotatedclockwise. Rotation is limited to 45 degrees by set screws 230 coming toa stop against the clockwise end of slots 229. At this point lugs 225have fully engaged tool groove 112a on the interior of pack-off means100. On further rotation tool 200 and upper section 120 of pack-offmeans 100 move together for 30 degrees, being stopped by the end of slot1010 on upper section 120 coming to rest against pin 101k on ring 101.At this point the breech-locking means is disengaged and pack-off means100 may be pulled upwardly.

In the next step in preparing the well for temporary abandonment, the13%" riser 51 and back-off joint 53 are removed by first shearing ashear pin similar to shear pin 44, then rotating 30 degrees clockwise torelease the breech-locking means. After these are removed, pack-offmeans is run in the annular space between hangerhead 52 and hanger-head72 in the same manner as described for pack-01f means 100. Pack-offmeans 100 and 140 are similar to each other, the primary differencebeing only in diameters. However, the inside diameter in upper sectionwhich receives the running tool may be the same so that one running toolmay be used for different size pack-off units. At this point, thestructure is as shown in FIGURE 3.

Next, the 20" riser 31 and back-off joint 33 are re moved by rotating 30degrees clockwise, shearing the shear pin 44 and releasing thebreech-locking means as previously described.

A well cap 160, as shown in FIGURE 4, is then attached to thehanger-head 32 by means of the breechlocking means. As shown in FIGURE4, the well cap comprises a substantially tubular member having an upperclosed end to which a back pressure valve 163 is attached. Such backpressure valves, which comprise a kind of check valve adapted to beopened by a plunger from above, are well known in the art and need notbe de scribed further here. The lower end of the cap is provided withtooth segments 161 corresponding to the tooth segments 40 on back-offjoint 33 and therefore engageable with the tooth segments 41 of thehanger-head 32. An O-ring seal 162 around the well cap just above thetooth segments 161 sealingly engages the bore of hangerhead 32 toprovide a pressure tight joint when the well cap is fully engaged.Rotation of the well cap to the proper point of engagement of thecooperating teeth is assured by the stop slots 47 in the upper edge ofthe hanger-head 32 which are engaged by keys 164 disposed around thecircumference of the well cap and extending downwardly therefrom. Amilled slot 164a above the other end of slots 47 allows the insertion ofan additional key by a diver to prevent the cap from accidentallyrotating.

The cap 160 now serves as a protective housing for the underwater wellhead apparatus and well bore. Fresh water may be circulated in the wellbore until clear returns are received and lubricating oil may be pumpedin to displace the water in the well head. Back-pressure valve 163serves as a means of checking pressure before reentry.

The next step comprises removing the conductor riser 23 with its hub 22.This is done by sending a diver down to remove the bolts 25a holdingclamp 25. When the conductor riser has been lifted clear, the diverdrops into place the annular seal ring 164, which is of substantiallythe same diameter and external configuration as the flange 22a of thehub 22. An O-ring seal member 166 is provided between the face of member165 and the end of flange 24a, and an OTring 167 is provided between themember 165 and the hanger-head 32. A metal-to-metal seal is alsoafforded by the tapered extension 168 which fits within the taperedbevel 28 in the flange 24a. Following the insertion of the seal member165, the diver replaces the clamp 25. He may at this time also attachthe additional keys in slots 164a. The well is now entirely closed inand is ready for temporary abandonment.

When recompletion of the well is desired, the flexibility of this systemoffers two options, in that the well may be recompleted on bottom or atthe surface.

If recompleted on bottom, an underwater tubing head 170 as shown inFIGURE replaces pack-off means 100. At the same time, packoff 140 ispulled and replaced by pack-off 140a which has a large enough bore toclear the tubing head 170. It will be apparent that a different runningtool diameter will be required to set pack-off 140a.

Underwater tubing head 17 0 is secured to hanger-head 72 by thebreech-locking means previously described. Tooth segments 171, similarto the tooth segments on pack-off 100, are machined near the exteriorlower end of tubing head 170. At the base and below the tooth segmentsof tubing head 170, a sealing section 172, similar to lower section 130of pack-off means 100 (see FIG- URE 12), is telescopically and rotatablyattached by ball bearings as in pack-ofi means 100.

To install tubing head 170, it is lowered into position and rotateduntil the tooth segments line up with smooth segment portions onhanger-head 72. It is then pushed downwardly until the bottom tooth onits tooth segments contacts a shoulder 173 in hanger-head 72. As this isdone the sealing section will also be seated on a lower shoulder 174 inhanger-head 72 and will be compressed, sealing the annulus betweenhanger-heads 72 and 92. Tubing head 170 is then rotated 30 degreescausing full engagement of the breech-locking means.

The upper portion of the tubing head may be of conventional structure,however, a novel structure having particular advantages for remoteunderwater installations is shown in FIGURE 5. The tubing head thereshown is of generally tubular configuration and has a conventional sideoutlet 175 in communication with the annulus between the tubing and thecasing. The outlet 175 communicates with a bore 176 which terminatesabove the outlet 175 in an upwardly facing beveled support shoulder 177.The enlarged bore above the support shoulder 177 terminates at the topof the tubing head and has a straight smooth wall except whereinterrupted by a pair of circumferentially extending recesses 178 nearthe upper end of the bore.

The exterior of the upper end of the tubing head may be formed for anyconventional connection to a Christmas tree or other well head elementsbut a preferred form, as shown in the drawing, comprises a flange 179having a beveled back 180 suitable for use in a clamped connectionsimilar to that formed by clamp 25 as shown in FIGURE 2. A conventionalring groove 181 may be formed in the face of flange 179 for a sealingconnection to another well head element.

The drawing shows a tubing hanger 182 suitable for supporting a singlestring of tubing. It will be appreciated, however, that hangers adaptedfor supporting multiple strings of tubing might also be used.

The tubing hanger assembly shown has novel features which make itpeculiarly suitable for use in remote underwater installations. Thetubing (not shown) is connected by the usual threaded connection into acoupling 184 which is supported on an annular hanger ring 185 by theresting of a collar 136 on an upwardly facing support shoulder 187 inthe hanger ring. The hanger ring in turn rests upon the support shoulder177 of the tubing head. An upper extension 188 of the coupling issealingly engaged as by means of an O-ring 189 in a pack-off adapterring 190. The pack-off adapter ring has an annular clearance between itand the surrounding tubing head and a sandwich pack-oflf 191 is insertedbetween the pack-off ring and the tubing head. This sandwich pack-offstructure may be generally similar to pack-off 130 as shown in FIGURE12. The upper end of the pack-off comprises a tubular portion 192 whichhas a sliding fit in the tubing head and which is provided with aplurality of circumferentially distributed windows 193 through its wallsthrough which latch segment elements 194 are slidably received.

A latching sleeve 195 is telescopically received within the tubularportion 192 of the pack-0E and holds the latches 194 in place. Thelatching :sleeve is provided with a :beveled surface 196 which prior toengagement of the latches 194 is positioned in contact with the beveledsurfaces 194a on the latches. The latching sleeve has an annular recess197 immediately adjacent the beveled surface 196 to receive the latches194 prior to the movement of the latches into the latch recesses 178 andthe tubing head. Thus, it will be appreciated that to install thepackoff a handling tool engages the groove 199 in the upper end of thelatching sleeve and lowers the entire assembly into the tubing head. Atthis time the latches 194 are retracted into the annular groove 197 andthe pack-off is supported on the latching sleeve by means of cooperatingopposed collars 191a and 195a. This position is temporarily maintainedby shear pins passing through holes 192a in tubular portion 192 andholes 195b in collar 195a. When the pack-off has been positioned abovethe annulus between the ring and the bore of the tubing head, thelatching sleeve is pushed downwardly, after shearing the aforementionedshear pins, to force the packotf into the annulus and to force thelatches 194 into the latch grooves 178. To prevent latching sleeve frombeing inadvertently displaced a spring biased shear pin 19112 in collar191a is forced into a hole in latch sleeve 195. The pack-off is thuslatched into place and is held down by the latches 194.

To release and remove the pack-off, pin 191b is sheared by pullingupwardly on latch sleeve 195. This allows, on further upward motion oflatch sleeve 195, latches 194 to spring out of engagement. The pack-offmay then be removed, cooperating collars 191a and 195a resting againsteach other and transmitting upward force to the pack-off.

If, instead of completing at the bottom, the well is to be recompletedat the surface, the Well cap 160 will be removed, first testing forpressure in the well through back-pressure valve 163. All risers andback-off joints will be replaced as pack-off means are removed. The reverse procedure as for abandonment is followed. A standard well head isused at the surface except that no casing hangers but only pack-offs,are required in it. If desired only some of the strings may bere-connected. This may require a special pack-off means to replace astandard one to allow for passage of casing.

If the well is to be permanently abandoned, substantially the sameprocedure will be followed as in temporary abandonment. However, nopack-off means will be installed and before removing the conductor riserall casings will be plugged and cut or blown off below the mudline. Theconductor riser may then be removed having the well head and allhanger-heads attached thereto. This allows recovery of all apparatus inthe underwater well head.

While preferred embodiments of the invention have been shown anddescribed, many modifications thereof can be made by one skilled in theart without departing from the spirit of the invention and it isintended to protect by Letters Patent all forms of the invention fallingWithin the scope of the following claims.

We claim:

1. A method of completing an underwater well comprising the steps oflocating drilling means at an underwater well site,

installing conductor pipe with a well head atttached above the mudline,

attaching to said well head a conductor riser extending above the watersurface with landing base being attached thereto,

drilling holes for other casings,

suspending said other casings with risers attached thereto in said wellhead by hanger-heads,

cementing said other casings in place by circulating through said otherrisers and casings and through integral passage means in saidhanger-heads,

testing the well,

removing said other risers,

installing pack-off means in the annular spaces between saidhanger-heads,

removing said conductor riser and landing base,

attaching a well cap to said well head, and

temporarily abandoning said well.

2. The combination of claim 1 and including the steps of removing saidwell cap,

reinstalling said conductor riser and landing base attached thereto,

removing said pack-off means,

reinstalling said other risers,

installing casing head and control equipment,

installing a tubing head and a surface pack-off,

running tubing,

installing surface production tree, and

bringing in said well.

3. The combination of claim 1 including the steps of removing said wellcap,

installing an underwater tubing head,

running tubing and pack-off,

installing an underwater production tree, and

bringing in said well.

4. Well completion apparatus comprising a conductor pipe,

underwater well head means connected to said connected to said conductorpipe,

hanger-head means concentrically positioned in and supported by saidwell head means,

other casing means suspended from said hanger-head means, and

pack-01f means installed in annular spaces between said hanger-headmeans removable from said spaces on rotating less than one revolutionrelative to said hanger-head means.

5. The combination of claim 4 in which at least one of said hanger-headmeans is solely supported on the surrounding hanger-head means by latchmeans on the exterior thereof,

said latch means having a plurality of latch segments radially movablein a circumferential segment groove,

the outer face of said latch segment being correlatively shaped toengage cooperating support surfaces on the interior of said surroundinghanger-head means, and

means resiliently urging said latch segments into engagement with saidcooperating support surfaces.

6. Well completion apparatus comprising a conductor pipe,

underwater well head means connected to said conductor pipe,

hanger-head means concentrically positioned in and supported by saidwell head means,

other casing means suspended from said hanger-head means, and

pack-off means installed in annular spaces between said hanger-headmeans at least one of said hanger-head means having fluid passage meansintegrally disposed in the wall thereof,

said fluid passage means terminating in upper and lower openings on theinterior of said one hangerhead means,

support means being provided on the interior wall of said onehanger-head means between said upper and lower openings to supportanother hanger-head means concentrically therewithin.

7. A method of completing an underwater well comprising the steps oflocating drilling means at an underwater well site,

installing conductor pipe with a well head attached above the mudline,

attaching to said well head a conductor riser extending above the watersurface with landing base being attached thereto,

drilling holes for other casings,

suspending said other casings with other risers attached thereto in saidwell head by hanger-heads,

cementing said other casings in place by circulating through said otherrisers and casings and through integral passage means in saidhanger-heads,

testing the well,

removing said other risers,

installing pack-off means in the annular spaces between saidhanger-heads,

installing underwater tubing head,

running tubing and pack-off,

removing said conductor riser and attached landing base,

installing underwater production tree, and

bringing in the well.

8. Well completion apparatus comprising a conductor pipe,

underwater well head means connected to said conductor pipe,

a plurality of hanger-heads concentrically positioned in and supportedby said well head means with annular spaces there'between,

other casing means suspended from each of said hanger-heads,

underwater tubing head means connected in one of said annular spacesbetween said hanger heads,

pack-off means installed in the other annular spaces between saidhanger-heads,

tubing suspended from said underwater tubing head means, and

production tree means connected to said tubing head.

9. The combination of claim 8 in which at least one of said hanger-headshas a latch means on the exterior thereof,

said latch means having a plurality of latch segments radially movablein a circumferential segment groove,

the outer face of said latch segments being correlatively shaped toengage cooperating support surfaces on the interior of a surroundinghanger-head,

and means resiliently urging said latch segments into engagement withsaid cooperating support surfaces.

10. Well completion apparatus comprising first generally tubularhanger-head means,

second generally tubular hanger-head means concentrically disposedwithin said first hanger-head means with an annular space therebetween,

and a tubing head supported on said first hanger-head means by areleasable connection and having a portion sealingly received betweensaid hanger-head means.

11. Well completion apparatus as defined by claim wherein saidreleasable connection by which said tubing head is supported on saidfirst hanger-head means comprises a breech-block connection.

12. Well completion apparatus as defined =by claim 10 wherein said firsthanger-head means has an upwardly facing internal shoulder,

said portion of said tubing head has a longitudinally compressibletubular packoff, and

said packotf engages said shoulder and is compressible between saidshoulder and said releasable connection.

13. Well completion apparatus as defined by claim 10 and including ametal-to-metal seal connection between said tubing head and said firsthanger-head means which comprises an external taper on said tubing head,and

a corresponding internal taper in said first hanger-head means,

said tapers being sealingly engaged by the engagement of said releasableconnection.

14. Well completion apparatus comprising a conductor pipe,

an underwater well head connected to said conductor a conductor riserconnected to said underwater well head,

a landing base connected to the upper end of said conductor riser abovethe water surface,

a hanger-head concentrically positioned in and supported by said wellhead,

another casing suspended from said hanger-head,

a releasable back-ofi connected to said hanger-head, and

another riser conected to said hanger-head, said other riser extendingabove the water surface.

15. The combination of claim 14 in which said hangerhead and saidback-01f are connected by a breech-block connection.

16. The combination of claim 14 in which said hangerhead and saidback-01f are connected by a breech-block,

said breech-block comprising circumferentially disposed tooth segmentmeans on the interior of said hangerhead and correspondingcircumferentially disposed tooth segment means on the exterior of saidback-off, said tooth segment means being alternate rows of no lead angleteeth and smooth wall portions, and

cooperating stops on said hanger-head and said backoiT to limit theirrelative rotation.

17. The combination of claim 14 in which said hangerhead has a fluidpassage integrally disposed in the walls thereof, said fluid passageterminating in upper and lower openings on the interior of saidhanger-head, and

support means provided on the interior walls of said hanger-head betweensaid upper and lower openings adapted to support another hanger-headconcentrically therewithin.

18. The combination of claim 17 and including another concentricallydisposed hanger-head supported on said support means, and in which saidother hanger-head has a latch means on the exterior thereof,

said latch means having a plurality of latch segments radially movablein a circumferential segment groove,

the outer face of said latch segments being correlatively shaped tomatch the surfaces of said support means on the interior of thesurrounding hangerhead,

and means resiliently urging said latch segments into engagement withsaid support means.

19. Pipe suspension apparatus comprising tubular hanger-head means,

pipe connection means at the lower end of said hangerhead means,

support means on the exterior of said hanger-head means for supportingit on a surrounding element,

means for allowing fluid flow from below said hanger- 'head means toabove it,

and a sealing breech-block connection at the upper end of saidhanger-head means,

said breech block connecting comprising circumferentially disposed toothsegment means on the interior of said hanger-head, said tooth segmentmeans being alternate rows of no lead angle teeth and smooth wallportions.

20. The combination of claim 19 and including tubular back-01f means,

said back-off means being attached to said hanger head means bycorresponding rows of no lead angle teeth on its exterior engaging saidhanger-head means teeth, said back-off means and hanger-head means beingdisengageable on rotation of said back-off means no more than one-halfof a revolution, and

pipe connections means on the upper interior of said back-off means.

21. Pipe suspension apparatus comprising tubular hanger-head means,

pipe connection means at the lower end of said hanger-head means,

support means on the exterior of said hanger-head means for supportingit on a surrounding element,

means for allowing fluid flow from below said hangerhead means to aboveit,

tubular back-off means attached to said hanger-head means by abreech-block connection,

said breech-block connection being held in full engagement by shearmeans,

including interchangeable key and stop means on said back-off means, and

positioned to allow relative rotation of said back-off means and saidhanger-head means from engaged position to disengaged position uponshearing of said shear means.

22. The combination of claim 21 and including a tapered surface on theexterior of said back-off means below said breech-block connection,

a cooperating tapered surface on the interior of said hanger-head meansto form primary metal-to-metal seal means, and

an O-ring seal between said back-off means and said hanger-head meansadjacent said primary seal means.

23. Pipe suspension apparatus as defined by claim 19 and includingsupport means on the interior of said hanger-head means, and

fluid passage means formed in the wall of the hangerhead means withopenings into the interior thereof above and below said interior supportmeans.

24. The combination of claim 23, and including tubular back-off means,

said back-ofl means being attached to said hanger-head means by saidbreech-block connection, and

pipe connection means in the form of threads on the upper interior ofsaid back-off means.

25. The combination of claim 24 in which said breech-block connection isheld in full engagement by shear means, and

including interengageable key and stop means on said 17 back-oil meansand said hanger-head means positioned to allow relative rotation of saidback-01f means and said hanger-head means from engaged position todisengaged position upon shearing of said shear means. 26. Thecombination of claim 25 and including a tapered surface on the exteriorof said back-off means below the breech-block connection, and

a cooperating tapered surface on the interior of said hanger-head meansto form a primary metal-to-metal seal means, and

an O-ring seal between said back-off means and said hanger-head meansadjacent said primary seal means.

27. Pipe suspension apparatus as defined by claim 19 wherein saidsupport means comprises radially extensible latch means.

28. The combination of claim 27 and including passage means integrallydisposed in the Walls of said hanger-head,

said passage means having upper and lower openings on the interior ofsaid hanger-head means,

latch support means on the interior of said hanger-head means locatedbetween said upper and lower openings of said passage means.

29. The combination of claim 27 and including tubular back-off means,

said back-off means being attached to said hanger-head means by saidbreech-block connection, and

pipe connection means in the form of threads on the upper interior ofsaid back-oil means.

30. The combination of claim 29 and including a tapered surface on theexterior of said back-off means below said breech-block connection, and

a cooperating tapered surface on the interior of said hanger-head meansto form primary metal-to-metal seal means, and

an O-ring seal between said back-off means and said hanger-head meansadjacent said primary seal means.

31. A hanger-head for supporting a pipe in a well having a generallytubular shape,

fluid passage means integrally disposed in the walls thereof,

said fluid passage means having upper and lower openings into theinterior of said hanger-head means, and pipe support means on theinterior of said hanger-head means,

said support means being between said upper and lower openings.

32. The combination of claim 31 in which tooth segment means arecircumferentially disposed on the upper interior of said hanger-headmeans,

said tooth segment means being in the form of alternate longitudinalrows of teeth and smooth surface segmerits, said teeth having no leadangle.

33. The combination of claim 32 and including tubular back-off means,

releasably attached to said hanger-head means by breech-locking means,

said breech-locking means being the combination of said tooth segmentmeans in the upper interior of said hanger-head means and correlativetooth segment means on the exterior of said back-off means, and

pipe connection means being located on the upper interior of said back-Emeans.

34. First tubular hanger-head means,

said hanger-head means having fluid passage means integrally disposed inthe walls thereof,

said fluid passage means having upper and lower openings into theinterior of said hanger-head means, and latch support means on theinterior of said hanger-head means,

said openings being located above and below said latch support means,

said latch support means being in the form of at least one groovecircumferentially formed on the interior wall of said first hanger-headmeans,

the bore of said hanger-head means being substantially straight exceptfor said latch support means, and

second tubular hanger-head means with latch means on the exterior ofsaid second hanger-head means engaged with said latch support means.

35. The combination of claim 34 in which said latch means are aplurality of latch segments radially movable in a circumferentialsegment groove on said second hanger-head means,

the outer face of said latch segments being correlatively shaped tomatch the surfaces of said latch support means on the'interior of saidfirst hanger-head means, and

means resiliently urging said latch segments into engagement with thelatch support means.

36. Well apparatus comprising,

first tubular hanger-head means,

first support means on the interior of said first hangerhead means,

second tubular hanger-head means concentrically disposed within saidfirst hanger-head means,

said second hanger-head means having second support means on theexterior thereof cooperating with said first support means on theinterior of said first hanger-head means,

fluid passage means between the first and second hangerhead meansincluding an annular space at the upper end thereof,

pack-ofi means installed in said annular space,

said pack-01f means having attachment means thereon to connect it to oneof said hanger-head means, and

seal means rotatably connected to said attachment means,

said pack-off means sealing said annular space between said first andsecond hanger-head means.

37. A well pack-ofl means comprising attachment means for releasablyattaching said packoff means to a surrounding support member, and

tubular seal means rotatably attached to the base of said attachmentmeans.

38. A well pack-off means as defined by claim 37,

wherein said attachment means comprises circumferentially disposedlongitudinal rows of arcuate teeth of no lead angle with smooth surfacearcs between the rows.

39. A well pack-ofi means as defined by claim 37, and

including a tapered portion on said attachment means adapted to engage acorresponding tapered portion on a surrounding element to form ametal-to metal seal.

40. A well head means comprising upper hub means, said upper hub meansbeing generally cylindrical with a cylindrical passage therethrough andhaving a flange portion at its base,

lower hub means being generally cylindrical and having a cylindricalpassage therethrou-gh, said lower hub means having a flange portion atits upper end,

clamp means engaged with and holding together said flange portions ofsaid upper and lower hub means,

support means on the interior of said lower hub means,

first seal means of the met-al-to metal type comprising a beveledshoulder on the upper interior of said lower hub means and a downwardlytapered conical lip at the base of said upper hub means, said beveledshoulder and said tapered conical lip being in full circumferentialcontact,

second seal means of the resilient type between said flanges, and

pipe connection means at the base of said lower hub means and the upperend of said upper hub means.

(References on following page)

